Semiconductor light-emitting device and method of manufacturing the same and mounting plate

ABSTRACT

To offer a semiconductor light-emitting device capable of preventing a short circuit failure caused by adhesion of the solder, change of a beam shape, and decrease of a beam output. A semiconductor laser device  1  is manufactured by overlaying a laser chip having a p-side electrode and a n-side electrode in a crystalline substrate and a mounting plate having a first solder film and a second solder film in a supporting body. The laser chip has a level difference A such that the p-side electrode is projected beyond the n-side electrode. The mounting plate has a level difference B such that the first solder film is projected beyond the second solder film. The level difference B of the mounting plate is determined as higher than the level difference A of the laser chip. Therefore, when the mounting plate is overlaid to the laser chip, first, the n-side electrode contacts with the second solder film, and then, the p-side electrode contacts the first solder film. Accordingly, even if the solder is squeezed out in the vicinity of the n-side electrode, the solder is hardly squeezed out in the vicinity of the p-side electrode. The pn junction part is generally positioned in the vicinity of the p-side electrode, which controls the solder to adhesion to the pn junction part.

The present application is a continuation of U.S. patent applicationSer. No. 10/217,498, filed Aug. 14, 2002, now U.S. Pat. No. 6,761,303,which in turn is a continuation of U.S. patent application Ser. No.09/729,213, filed Dec. 5, 2000, now U.S. Pat. No. 6,474,531.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor light-emitting deviceincluding a semiconductor chip having a pair of electrode films in thesame side of a mounting plate, to a method of manufacturing the same,and to a mounting plate used for the method thereof.

2. Description of the Related Art

In recent years, semiconductor light-emitting devices including asemiconductor laser device in which a nitride semiconductor such as GaNis employed as a light source for short-wavelength light have beendeveloped. Generally, with the semiconductor laser device utilizing thenitride semiconductor, an n-type layer, an active layer and a p-typelayer, which are made of the nitride semiconductor are stacked insequence on a substrate made of sapphire (Al₂O₃). Among a pair ofelectrode films of the semiconductor laser device, a p-side electrode isformed on the p-type layer which is the most upper layer in thesemiconductor layer, while an n-type electrode is formed on the n-typelayer which is exposed by etching the p-type layer and the active layer.Hence, the substrate, the semiconductor layer, the p-side electrode andthe n-side electrode are collectively called a semiconductor chip.

In the semiconductor light-emitting device, the semiconductor chip ismounted on a mounting plate called a submount. The semiconductor chip ismounted on the mounting plate in a state, in which a side of thesemiconductor layer is opposed to the mounting plate in order to scatterheat generated in the semiconductor layer effectively. The mountingplate has a pair of lead electrode layers formed in a side where thesemiconductor chip is mounted thereon, and a solder film is formed onthe lead layers. After mounting the semiconductor chip on the mountingplate, the p-side and the n-side electrodes of the semiconductor chiprespectively contact with a pair of the lead electrode layers via thesolder film.

However, in the conventional semiconductor light-emitting device, whenthe semiconductor chip is worn on the submount, the pressed solder filmwith the p-side and the n-side electrodes of the semiconductor chip issqueezed out to the side of the solder layer. Then, the squeezed-outsolder may adhere to a pn junction part of the semiconductor chip, whichcauses the short circuit failure.

Additionally, the squeezed-out solder may adhere to a vicinity of anejection part of a laser beam. In such a case, a shape of the laser beamchanges, and what's worse, an optical-power output decreases. If a shapeof the laser beam changes as mentioned before, specifically, when thissemiconductor light-emitting device is applied to an optical diskapparatus and so on, it leads to less tracking accuracy. On top of that,such decrease of the optical-power output of the laser beam causesincrease of heating value, because a large amount of current must beflowed to the semiconductor chip in order to acquire rated output.

SUMMARY OF THE INVENTION

The invention has been achieved in consideration of the above problemsand its object is to provide a semiconductor light-emitting devicecapable of preventing the short circuit failure in the pn junction partcaused by adhesion of the solder, change of a beam shape, and decreaseof an optical-power output and a method of manufacturing the same and amounting plate.

A method of manufacturing a semiconductor light-emitting deviceaccording to the present invention comprises a step of overlaying afirst and second electrode films of a semiconductor chip to apredetermined supporting body by using a first solder film and a secondsolder film, and in the semiconductor chip, a surface of the firstelectrode film is projected beyond a surface of the second electrodefilm in a manner that the deformation amount of the second solder filmis larger than that of the first solder film.

Other methods of manufacturing semiconductor light-emitting devicesaccording to the present invention comprises a step of overlaying thefirst and second electrodes to the first and second solder films of amounting plate. A semiconductor provides a level difference such that asurface of the first electrode is projected beyond that of the secondelectrode therebetween. A mounting plate provides a level differencesuch that a surface of the first solder film is projected beyond asurface of the second solder film therebetween, and the level differencein the mounting plate is determined in a manner to be higher than thatof the semiconductor chip.

A mounting plate according to the present invention is provided with thesupporting body, the first and second solder films formed in the sameside of the supporting body. Between the first solder film and thesecond solder film, a level difference is formed such that the surfaceof the first solder film is projected beyond that of the second solderfilm and is higher than that of the semiconductor chip.

A semiconductor light-emitting device according to the present inventioncomprises the semiconductor chip having the first and second electrodesin the same side of the mounting plate, and the mounting plate havingthe first and second solder films in the same side of the supportingbody. The semiconductor chip includes the level difference such that thesurface of the first electrode film is projected beyond that of thesecond film therebetween. The mounting plate provides the leveldifference such that the surface of the first solder film is projectedbeyond that of the second solder film therebetween. The supporting bodyhas a trench formed in an opposite side to the second solder film assandwiching the first solder film.

Further, another mounting plate according to the present invention hasthe first and second solder films in the same side of the supportingbody and provides the level difference such that the surface of thefirst solder film is projected beyond that of the second solder filmtherebetween. The supporting body has a trench formed in an oppositeside to the second solder film as sandwiching the first solder film.

Furthermore, another method of manufacturing a semiconductorlight-emitting device according to the present invention comprises astep of overlaying the first and second electrodes of the semiconductorchip to the first and second solder films of the mounting plate. Thesemiconductor chip provides the level difference such that the surfaceof the first electrode is projected beyond that of the second electrode.The mounting plate provides the level difference such that the surfaceof the first solder film is projected beyond that of the second solderfilm. An outline of the first solder film in a contact surface betweenthe first electrode and the first solder film is positioned inwardlyfrom an outline of the first electrode in the contact surface, at leastin a specific direction.

In the method of manufacturing a semiconductor light-emitting device,another method of manufacturing the semiconductor light-emitting device,or the mounting plate according to the present invention, when thesemiconductor chip is overlaid to the mounting plate, the firstelectrode contacts with the first solder film. Accordingly, even ifsolder of the second solder film is squeezed out, solder of the firstsolder film is prevented squeezing out. The pn junction part of thesemiconductor chip is generally disposed in a side of the firstelectrode having an amount of projection larger than the other; hence,the solder may be prevented from adhering to the pn junction part.

In the semiconductor light-emitting device or other mounting platesaccording to the present invention, the supporting body has the trenchformed in the opposite side of the second solder film as sandwiching thefirst solder film. In case that the solder of the first solder film issqueezed out, the solder flows into the trench, which prevents thesolder from adhering to the pn junction part. (The pn junction part isgenerally disposed in the vicinity of the first electrode film.)

In the other method of manufacturing a semiconductor light-emittingdevice, an outline of the first solder film in contact surfaces of thefirst electrode film and the first solder film is positioned inwardlyfrom an outline of the first electrode film (at least in a specificdirection). Hence, even the first solder film is applied to pressure,the solder is hardly squeezed out from the out side of the outline ofthe first electrode film. Accordingly, the solder film is prevented fromadhering to the pn junction part of the semiconductor chip.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome clear from the following description of the preferred embodimentsgiven with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view showing a semiconductor applied to asemiconductor laser device of the first embodiment in the presentinvention;

FIG. 2 is a cross sectional view showing a structure of a laser chip ofthe semiconductor shown in FIG. 1;

FIG. 3 is a cross sectional view showing a structure of a mounting plateof the semiconductor shown in FIG. 1;

FIGS. 4A and 4B are a cross sectional views in every step forexplanation of a method of manufacturing the semiconductor laser deviceshown in FIG. 1;

FIG. 5 is a cause and effect diagram for explanation of the effect ofthe first embodiment;

FIG. 6 is a cross sectional view for explanation of the major part ofthe semiconductor laser device relative to the second embodiment in thepresent invention;

FIG. 7 is a cross sectional view for explanation of the major part ofthe semiconductor laser device relative to the third embodiment in thepresent invention;

FIG. 8 is a VIII—VIII line arrow sectional view in FIG. 7; and

FIG. 9 is an IX—IX line arrow cross sectional view in FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described in detail hereinbelow byreferring to the drawings.

First Embodiment

FIG. 1 shows one example of a semiconductor light-emitting device 100 inwhich a semiconductor laser device is employed according to a firstembodiment. The semiconductor light-emitting device 100 comprises thesemiconductor laser device 1 inside a predetermined-shape package. Thepackage 10 includes a supporting disk 11, a cylindrical lid 12 to beattached to the supporting disk 11. One end of the cylindrical lid 12 isclosed but has a window 12A through which a laser beam emitted from thesemiconductor laser device 1 passes to the outside of the package 10.The lid 12 is made of a metal such as copper (Cu) or iron (Fe) and thewindow 12A is made of a transparent glass or resin. Here, thesemiconductor laser device 1 corresponds to one specific example of asemiconductor laser device of the present invention.

The supporting disk 11 contains metal such as copper or iron, and on itssurface (a front of FIG. 1), a rectangular-shaped placing board 15 isformed integrally. The semiconductor laser device 1 is provided with amounting plate 30, which is a board-shaped member and fixed on theplacing board 15, and a laser chip 20 formed thereon. The placing board15 and the mounting plate 30 support the laser chip 20, and at the sametime, have a role for scattering heat of the laser chip 20. Thesupporting disk 11 is provided with a pair of pins 17 and 18, whichmaintains insulation with respect to the supporting disk 11, and isrespectively-connected through a wire W to lead electrode layers 32 and33 described after. Additionally, the placing board 15 and the mountingplate 30 are also called a heat sink and a submount respectively. Here,the laser chip 20 corresponds to a specific example of a semiconductorchip in the present invention.

FIG. 2 is a cross sectional view showing a structure of the laser chip20. The laser chip 20 includes a crystalline substrate 21 made ofsapphire (Al₂O₃). The crystalline substrate 21 may be made of spinel(MgAl₂O₄), gallium nitride (GaN), silicon (Si), or silicon carbide (SiC)instead of sapphire. Formed on a surface of the n-type contact layer 22is about 4 μm in thickness, for example. Formed on a surface of then-type contact layer 22 is an n-type cladding layer 23 made of n-typeAlGaN in which n-type impurities, e.g., silicon is doped. The thicknessof the n-type contact layer 22 is an n-type cladding layer 23 is about1.2 μm in thickness, for example.

An active layer 24 made of InGaN is formed on a surface of the n-typecladding layer 23. The active layer 24 having a light-trapping layeracts as a so called light-emitting layer. Formed on a surface of theactive layer 24 is a p-type cladding layer 25 made of p-type AlGaN inwhich p-type impurities, e.g., Mg is doped. The thickness of the p-typecladding layer 25 is about 0.8 μm, for example. Formed on a surface ofthe p-type cladding layer 25 is a p-type contact layer 26 made of p-typeGaN in which p-type impurities, e.g., Mg is doped. The thickness of thep-type contact layer 26 is about 0.3 μm, for example. A part of thep-type cladding layer 25 and the p-type cladding layer 26 is etched. Arestricting layer 27 made with an insulating film such as silicon oxideor alumina (Al₂O₃), is provided so as to sandwich the p-type claddinglayer 25 and the p-type contact layer 26.

Formed on a surface of the p-type contact layer 26 is the p-sideelectrode 2A. The p-side electrode 2A is alloyed by sequentiallystacking a nickel (Ni) layer and a gold (Au) layer from the side of thep-type contact layer 26 and then applying heat thereon, for example. Apart of the n-type contact layer 22, the n-type cladding layer 23, theactive layer 24, the p-type cladding layer 25 and the p-type contactlayer 26 is etched and the n-type contact layer 22 is partly exposed.The n-side electrode 2B is formed on the exposed surface of the n-typecontact layer 22. The n-side electrode 2B is alloyed, for example, bysequentially stacking a titanium (Ti) layer, an aluminum (Al) layer anda gold layer from the side of the n-type contact layer 22 and thenapplying heat thereon. The p-side electrode 2A and the n-side electrode2B are formed in a belt-like shape extending in a directionperpendicular to the sheet of FIG. 2. The difference in height betweenthe surface of the p-side electrode 2A and the surface of the n-sideelectrode 2B is about 3.5 μm, for example.

The surface of the p-side electrode 2A and that of the n-side electrode2B are parallel to the surface of the crystalline substrate 21. Thep-side electrode 2A is projected higher beyond the n-side electrode 2B,for example 2.7 μm. That is, a level difference represented as code A inthe figures between a surface of the p-side electrode 2A and a surface Bof the n-side electrode 2B is, for instance, 2.7 μm. Here, the p-sideelectrode 2A corresponds to an example of the first electrode film inthe present invention. The n-side electrode 2B corresponds to a specificexample of a second electrode film in the present invention.

The laser chip 20 has a pair of unillustrated reflecting mirrors in theboth edges in a vertical direction relative to the figure. The mirrorshave a structure overlaid a silicon dioxide layer and a zirconium oxide(ZrO) layer in turn, and formed in a manner that reflectivity ofreflective mirror film is lower than that of the other. Light generatedfrom the active layer 24 is amplified to and fro a pair of thereflective films, then emitted from one reflective mirror film as alaser beam.

FIG. 3 is a cross sectional view showing a structure of the mountingplate 30. The mounting plate 30 comprises lead electrode layers 32 and33, solder films 4A and 4B on a supporting body 31, which is aboard-shaped member with a rectangular shape. The supporting body 31 ismade of insulating material with high thermal conductivity such asdiamond, beryllium oxide (BeO), copper-tungsten (CuW), aluminum nitride(AlN), cubic boron nitride (cBN), silicon (Si), or silicon carbide(SiC). The size of mounting plate 30 is for instance, 200 μm ofthickness, 0.6 mm of width (length in a left-right direction in thedrawings), and 1 mm of depth (length in a depth direction in thedrawings).

A surface of the supporting body 31 is a flat surface. A pair of thelead electrode layers 32 and 33 whose thickness is, for example, 10 μm,is formed thereon. The lead electrode layers 32 and 33 can be formedwith gold or gold-tin alloy. The lead electrode layers 32 and 33 mayhave the structure of subsequently stacking a titanium layer, a platinumlayer and a gold layer from the side of the mounting plate 30. As seenin FIG. 1, those lead electrodes 32 and 33 are electrically connected toa pair of the pins 17 and 18 disposed in the supporting disk 11 (FIG. 1)through the wire W respectively. Between both lead electrode layers 32and 33, there is provided approximately a 50-μm interval. The leadelectrode layers 32 and 33 correspond to examples of a first leadelectrode layer and second electrode layer in the present invention.

The first solder film 4A and the second solder film 4B are formed on thelead electrode layers 32 and 33 of the mounting plate 30. The first andsecond solder films are formed with low-melting point metal such as tin,gold-tin alloy, tin-silver alloy (SnAg), indium-tin alloy (InSn) andindium (In). A thickness of the first solder film is 3.5 μm and that ofsecond solder film 4B is 7 μm. That is, the level difference B betweensurfaces of the first solder film 4A and the second solder film 4B is3.5 μm. The first and second solder films 4A and 4B respectivelycorrespond to specific examples of “first and second solder films” inthe present invention.

[Method of Manufacturing Semiconductor Laser Device]

Next, A method of manufacturing a semiconductor laser device of theembodiment will be explained.

First, as shown in FIG. 2, the n-side contact layer 22 made of n-typeGaN, the n-type cladding layer 23 made of n-type AlGaN, the active layer24 made of GalnN, the p-type cladding layer 25 made of p-type AlGaN, andthe p-side contact layer 26 made of p-type GaN are grown in sequence onthe surface of the crystalline substrate 21 made of, e.g., sapphire withMOCVD (Metal Organic Chemical Vapor Deposition).

After growing layers from the n-side contact layer 22 to the p-sidecontact layer 26, the p-type contact layer 26 and the p-type claddinglayer 25 are partly etched with a lithography method and the restrictinglayer 27 made with, e.g., an insulating material is formed thereon.Subsequently, the p-side contact layer 26, the p-type cladding layer 25,the active layer 24 and the n-type cladding layer 23 are selectivelyremoved to expose the n-side contact layer 22. Thereafter, the n-sideelectrode 2B is selectively formed on the exposed area of the n-sidecontact layer 22 and then the p-side electrode 2A is selectively formedon the p-side contact layer 26.

After forming the p-side electrode 2A and the n-side electrode 2B, thecrystalline substrate 21 is cut vertically to the direction along thelength of the p-side electrode 2A (in a vertical direction to the sheetof FIG. 8) with a predetermined width. After that, a pair of reflectingmirror films is formed on a pair of side surfaces of the cutsemiconductor layer, respectively, and then the crystalline substrate 21is cut parallel to along the length of the p-side electrode 2A with apredetermined width. Thus, the laser chip 20 is formed. As shown in FIG.2, the level difference A (2.7 μm) is provided between the surfaces ofthe p-side electrode 2A and the n-side electrode 2B of this laser chip.

Following this, the lead electrode layers 32 and 33 are formed on thesurface of the supporting body 31 with plating, sputtering or vacuumevaporation. Then, the first solder film 4A and the second solder film4B are formed with vacuum evaporation on the surfaces of the leadelectrode layers 32 and 33. This procedure forms the mounting plate 30.The level difference (3.2 μm) is provided between the surfaces of thefirst solder film 4A and the second solder film 4B of the mounting plate30.

As shown in FIG. 4A, the laser chip is overlaid to the mounting plate 30in an up-down state and the p-side electrode 2A and the n side electrode2B contact with the first solder film 4A and the second solder film 4B.Then, an unillustrated applying pressure apparatus applies pressure onthe laser chip 20 and the mounting plate 30, for instance, with 5 g. ofpressure power. This applying pressure is performed while keeping aparallel state between bases of the laser chip (a surface in FIGS. 4Aand 4B) and the mounting plate 30. Further, the first solder film 4A andthe second solder film 4B are heated and softened at about 280° C. Thisheating is preferably performed in an atmosphere of nitrogen gas orwater gas, or in a mixture atmosphere of those gases to preventoxidizing the first and second solder films 4A and 4B.

The level difference B (3.5 μm) of the mounting plate 30 is higher thanthe level difference A (2.7 μm) of the laser chip 20. For this reason,in case that the laser chip 20 and the mounting plate 30 are overlaidand applied to pressure, firstly, the n-side electrode 2B contacts withthe second solder film 4B, then the p-side electrode 2A contacts withthe first solder film 4A. This means that the deformation amount of thefirst solder film 4A (in an applying pressure direction) is smaller thanthat of the second solder film 4B. Thus, as shown in FIG. 4B, the p-sideelectrode 2A is prevented from squeezing out in the vicinity of then-side electrode 2A even though the second solder film 4B is squeezedout in the vicinity of the n-side electrode 2B. As shown in FIG. 4B, themounting plate 30 and the laser chip 20 are overlaid as mentioned above.Additionally, the p-side electrode 2A and the n-side electrode 2B areelectrically connected to the lead electrode layers 32 and 33respectively.

After completion of overlaying the mounting plate 30 and the laser chip20, the back of the mounting plate 30 (an opposite side of the side ofthe laser chip) adheres to the placing board 15 formed integrally to thesupporting disk 11 (FIG. 1) with soldering. Then, the lead electrodelayer 32 of the mounting plate 30 is connected to the pin 17 through thewire W, and the lead electrode layer 33 is connected to the pin 18through the wire W. Finally, the lid 12 formed separately is disposed inthe supporting disk 11. This procedure forms the semiconductorlight-emitting device 100 shown in FIG. 1.

The effect of the embodiment will be described hereinafter. As shown inFIGS. 4A and 4B, the level difference B (3.5 μm) of the mounting plate30 is higher than the level difference A (2.7 μm) of the laser chip 20.Because of this, in case that the laser chip 20 and the mounting plate30 are overlaid in a parallel state and applied to heat, the n-sideelectrode 2B first contacts with the second solder film 4B, next, thep-side electrode 2A contacts with the first solder film 4A. Accordingly,even though the second solder film 4B opposed to the n-side electrode 2Bis squeezed out, the first solder film 4A opposed to the p-sideelectrode 2A is prevented from squeezing out. The pn junction part (or,stacking parts of the N-type cladding layer 23, the active layer 24 andthe p-type cladding layer 25) is provided in the vicinity of the p-sideelectrode 2A. Therefore, if the first solder film 4A in the side of thep-side electrode is not squeezed out, there is no short circuit failurein the pn junction part.

FIG. 5 is a cause and effect diagram showing a relationship of the shortcircuit failure and ratio between the level difference A in the laserchip 20 and the level difference B in the mounting plate 30. A pluralityof semiconductor laser devices 1 is formed by changing the ratio betweenthe level difference A in the laser chip 20 and that in the mountingplate 30. In each of the semiconductor laser devices, the yields of ashort circuit failure are observed. In FIG. 5, the yields 100% meansthat there is no short circuit failure.

It is known from FIG. 5 that when the ratio of the level difference B inthe mounting plate 30 relative to the level difference A in the laserchip 20, that is, B/A is larger than 1, the yields are greatly enhanced(this means that the short circuit failure dramatically reduced). As forthe reason of this, it is considered that when B/A is larger than 1, thefirst solder film 4A in a side of the p-side of electrode 2A is hard tobe squeezed out as shown in FIG. 4B.

In this technical field, as for the failure caused by the short circuitfailure of the pn junction part, it is generally said that yields morethan 80% are required. Thus, from FIG. 5, an expression: 1.2≦B/A≦3 ismuch preferable. The limitation value, 3 is determined from the reasonthat if B/A is larger than 3, a large amount of solder is squeezed outin the vicinity of the n-side electrode 51, which is not preferable.

In addition, in case that the yield more than 90% is required for theyields of the short circuit failure, from FIG. 5, an expression:1.3≦B/A≦2.5 is preferable.

As explained above, according to the embodiment, for the reason of whichthe level difference between the first solder film 4A and the secondsolder film 4B is higher than the level difference between the p-sideelectrode 2A and the n-side electrode 2B, even if the second solder film4B is squeezed out, the first solder film 4A is hardly squeezed out.Accordingly, the prevention of the short circuit failure in the pnjunction part can be attained. Additionally, the solder is preventedfrom squeezing out in the vicinity of the p-side electrode 2A, so thatthe problems described after can be solved. Such problems are: a beamshape is changed by adhesion of the solder to an emitting part of thelaser beam; and laser beam intensity decreases.

In case that the ratio of the level difference B of the mounting plate30 relative to the level difference A of the laser chip 20 is determinedas larger than 1.2 and lower than 3, the yields of the short circuitfailure in the pn junction part can enhance more than 80%. Furtherpreferably, in case that this ratio is determined as more than 1.3 andlower than 2.5, the yields of the short circuit failure in the pnjunction part can enhance to more than 90%.

In the embodiment, the level difference B can be determined by a simplemethod for the following reasons: a surface of the mounting plate 30becomes a flat surface; and the lead electrode layers 32 and 33 becomethe same thickness in order to determine the level difference B of themounting plate 30 by means of only a thickness of the first solder film4A and of the second solder film 4B. On top of that, a level differencepart may be provided with a surface itself of the mounting plate 30, orthe lead electrode layers 32 and 33 may have different thickness. Thesolder films may be formed as stacked films comprised of more than twolayers so as to change a thickness of a specific layer. Furthermore, inthe embodiment, the first solder film 4A and the second solder film 4Bare provided with the mounting plate 30, the solder films 4A and 4B maybe provided with the p-side electrode 2A and the n-side electrode 2B ofthe laser chip.

[Modification]

FIG. 6 is a view showing a modification of the laser chip in the firstembodiment. A laser chip 20A shown in FIG. 6 has the same configurationsas the laser chip of the first embodiment except shapes of the p-sideelectrode and the restricting layer. Hereinafter, the sameconfigurations as the first embodiment have the same numeral referencesand the detailed explanation will be omitted. The restricting layer 28relative to the modification is formed in a part in which the p-typecontact layer 26 and the p-type cladding layer 25 are removed byetching. This restricting layer 28 is also formed in a manner that itssurface does not reach the p-type contact layer 26. That is, the p-typecontact layer 26 has a structure which projects upwardly from therestricting layer 28. Additionally, the p-side electrode layer 29 of themodification is formed in a manner to cover the projected p-type contactlayer 26 and the front of the restricting layer 28 formed in the bothsides of the layer 26.

The semiconductor laser device shown in FIG. 1 can be achieved byoverlaying the laser chip 20A to the mounting plate 30 shown in FIG. 4.In the modification, in case that the level difference B between thefirst solder film 4A and the second solder film 4B of the mounting plate30 (FIG. 4) is higher than the level difference A of the laser chip 20A(a level difference between the top surface of the p-side electrode 29and the surface of the n-side electrode 28), which prevents the shortcircuit failure of the pn junction part occurring.

Second Embodiment

Next, the second embodiment of the present invention will be explained.FIG. 7 is a cross sectional view showing a main part of thesemiconductor laser device relative to the second embodiment. Thisembodiment has the same configuration as the first embodiment except aconfiguration of a mounting plate 30A. Hereinafter, the sameconfigurations have the same numeral references as the first embodimentand the detailed explanation will be omitted.

As shown in FIG. 7, on a surface of the mounting plate 30A, a trench 45is formed in the vicinity of the first solder film 4A opposed to thep-side electrode 2A. The trench 45 is formed in a position in which anopposite side of the second solder film 4B within the first solder film4A in between, as distinct from a position between the both solder films4A and 4B. The trench 45 is 50 μm of depth, 100 μm of width, and formedparallel to an extension direction of the p-side electrode 2A (aY-direction in the figure). That is, the trench 45 is formed extensivelyin a vertical direction relative to the figure. The trench 45 may beformed with a dicing saw and so on. The lead electrode layer 32positioned in a bottom of the first solder film 4A is formedsequentially to the inside of the trench 45 as maintaining almost thesame thickness. The trench 45 corresponds to a specific example of thetrench in the present invention.

In case that a direction parallel to the surface of the supporting body31 and at the same time, orthogonal to an extension direction of thep-side electrode 2A (the Y-direction in FIG. 7) is defined as aX-direction, a side edge surface C of the laser chip 20 is positioned ina center line between two side walls D of the trench 45 covered with thelead electrode layer 32. Accordingly, even if the first solder film 4Aopposed to the p-side electrode 2A is squeezed out, the squeezed-outsolder does not flow to the pn junction part of the laser chip 20, butflows into the trench 45 along the lead electrode layer 32. This furtherprevents form adhering the solder to the pn junction part of the laserchip 20.

As mentioned above, in the embodiment, the trench 45 is formed in thevicinity of the first solder film 41 opposed to the p-side electrode 2Ain the mounting plate 30, therefore, even if the solder is squeezed outfrom the side of the p-side electrode 2A, the squeezed-out solder issurely prevented adhering to the pn junction part. For this reason, theoccurrence of the short circuit failure is further controlled than inthe first embodiment. In addition, the lead electrode layer 32 under thefirst solder film 4A is formed sequentially to the inside of the trench45 so that the squeezed-out solder can be leaded to the inside of thetrench 45 effectively.

The second embodiment of the present invention also can be applied to acase that the level difference B between the first solder film 4A andthe second solder film 4B of the mounting plate 30 is shorter than thelevel difference A between the p-side electrode 2A and the n-sideelectrode 2B of the laser chip 20, or to a case that the leveldifferences A and B are the same size. On top of that, the trench 45 isformed in the vicinity of the first solder film 4A of the mounting plate30, which can allow the squeezed-out solder to flow into the trench,consequently, the short circuit failure of the pn junction part can becontrolled.

Third Embodiment

Finally, the third embodiment will be explained hereinafter. FIG. 8 is across sectional view showing the semiconductor laser device relative tothe third embodiment. FIG. 9 is an IX—IX line arrow cross sectional viewin FIG. 8. The third embodiment has the same configurations as the firstembodiment except a different shape of the first solder film 4A. Asdescribed below, the same configurations as the first embodiment havethe same numeral references and the detailed explanation will beomitted. In FIG. 8, a resonance direction of the laser chip 20, or, anextension direction of the p-side electrode 2A (an orthogonal directionrelative to a drawing in FIG. 8) is defined as a Y-direction. On theother hand, a direction parallel to a mounting plate 31 and at the sametime, vertical to the Y-direction is defined as an X-direction.

In the third embodiment, at least, in the X-direction, an outline C1 ofa contact surface (the top surface in FIG. 9) of the first solder film4A is positioned inwardly from an outline C2 of a contact surface (thebase surface in FIG. 9) of the p-side electrode 2A as shown in FIG. 9.More preferably, the size of the contact surface of the first solderfilm 4A is formed in a manner to be smaller than that of the contactsurface of the p-side electrode 2A. For the configuration as mentionedabove, when the laser chip 20 is overlaid to the mounting plate 30, evenif the first solder film 4A is deformed outwardly, the solder hardlyreaches the side edge surface of the p-side electrode 2A. Accordingly,adhesion of the solder to the pn junction part can be controlled.

Hereinbelow, an example of an effect of the embodiment will beexplained. The p-side electrode 2A is formed with a rectangular shape asshown in FIG. 9 and its long sides are determined as 700 μm, its shortsides are determined as 250 μm. On the other hand, the first solder film4A is formed with a rectangular shape as shown in FIG. 9 and its longsides are determined as 680 μm, its short sides are determined as 200μm. The outline C1 of the first solder film 4A is positioned inwardlyfrom the outline C2 of the p-side electrode 2A in the X-direction and ispositioned outwardly from the outline C2 of the p-side electrode 2A inthe Y-direction. In case that the laser chip 20 and the mounting plate30 are overlaid and occurrence of the short circuit failure in the pnjunction part of the laser chip 20 is observed, the yield of the shortcircuit failure is 98%. On the other hand, in case that the p-sideelectrode 2A and the first solder film 4A has the same shape of thecontact surface, that is, both solder films have a rectangular shapewhose long sides are 700 μm and short sides are 250 μm, and the outlinesof the p-side electrode 2A and the first solder film 4A are overlapped,the yield of the short circuit failure is 80%. This proves that theembodiment enhances the yield of the short circuit failure by 1.2 times.

In the embodiment, the outline C1 of the contact surface of the firstsolder film 4A may be positioned inwardly from the outline C2 of thep-side electrode 2A in the both X and Y-directions.

Moreover, the embodiment can be applied to the case that the leveldifference B between the first solder film 4A and the second solder film4B of the mounting plate 30 is shorter than the level difference Abetween the p-side electrode 2A and the n-side electrode 2B of the laserchip 20, or those level differences are the same size. The outline ofthe solder film 4A is positioned inwardly from the outline the p-sideelectrode 2A, which can control the solder not to be squeezed out theoutside of the p-side electrode 2A, thereby, the occurrence of the shortcircuit failure in the pn junction part can be prevented. Additionally,in the third embodiment, the trench 45 of the second embodiment may beformed in the mounting plate 30.

While the invention has been described with reference to specificembodiments chosen for purpose of illustration, it should be apparentthat numerous modifications could be made thereto by those skilled inthe art without departing from the basic concept and scope of theinvention. For example, the present invention is not limited by thesemiconductor but light emitting diode also can be applied. As for astructure of the semiconductor light-emitting device 100, variousstructures may be applied other than the structure shown in FIG. 1.

As has been explained above, according to the method of one aspect ofthe present invention, when the semiconductor chip and the mountingplate are overlapped within the first and second solder films inbetween, the deformation amount of the first solder film contacted withthe first electrode whose deformation amount is greater than the other,becomes smaller than that of the second solder film contacted with thesecond electrode film. Thus, the solder in the first electrode film ishardly squeezed out. Accordingly, the solder hardly adheres to the pnjunction part, which is generally disposed in the side of the firstelectrode film. This prevents the short circuit failure in the pnjunction part. Furthermore, the solder hardly adheres to the pn junctionpart, which prevents change of a beam shape and decrease of a beamoutput.

According to the method of manufacturing the semiconductorlight-emitting device, or the mounting plate of another aspect of thepresent invention, the level difference between the first and secondsolder films are higher than the level difference between the first andsecond electrode films. Therefore, when the semiconductor chip and themounting plate are overlapped, first, the second electrode film contactswith the second solder film, and then the first electrode film contactswith the first solder film. Hence, the solder hardly adheres to the pnjunction part, which is generally disposed in the first electrode filmside. This prevents the short circuit failure in the pn junction part.Further, the solder hardly adheres to the pn junction part, whichprevents change of a beam shape and decrease of a beam output.

According to the semiconductor light-emitting device, or mounting platethe supporting body of still another aspect of the invention, the trenchis formed in the opposite side of the second solder film within thefirst solder film in between. Therefore, even if the first solder filmis squeezed out, it flows into the trench, which prevents adhesion ofthe solder to the pn junction. Thereby, this can prevent the shortcircuit failure in the pn junction part accompanying by the squeezed-outsolder, change of a beam shape and decrease of a beam output.

According to the method of manufacturing the semiconductorlight-emitting device of further aspect of the present invention, atleast in a specific direction, the outline of the first solder film ispositioned inwardly from the outline of the first electrode film. Thiscontrols the first solder film not to be squeezed out from the outsideof the outline of the first electrode film, which prevents the shortcircuit failure in the pn junction part accompanying by the squeezed-outsolder, change of a beam shape, and decrease of a beam output.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

1. A semiconductor light-emitting device including a semiconductor chiphaving a first electrode film and a second electrode film in the sameside of a base and a mounting plate having a first solder film and asecond solder film in the same side of an insulating supporting body,wherein a level difference is provided in a manner that a surface of thefirst electrode film is projected beyond a surface of the secondelectrode film therebetween in the semiconductor chip; a leveldifference is provided in a manner that a surface of the first solderfilm is projected beyond a surface of the second solder filmtherebetween in the mounting plate; and a trench is formed in anopposite side of the second solder film sandwiching the first solderfilm in the insulating supporting body.
 2. A semiconductorlight-emitting device according to claim 1, wherein a first leadelectrode film and a second electrode film are formed respectivelybetween each of the first and the second solder films and the insulatingsupporting body.
 3. A semiconductor light-emitting device according toclaim 2, wherein the first lead electrode film extends inside thetrench.
 4. A semiconductor light-emitting device including asemiconductor chip, the semiconductor light-emitting device comprising:a base having thereon a first electrode film and a second electrodefilm; and an insulating supporting body having thereon a first solderfilm, a first lead electrode film, a second solder film, and a secondlead electrode film, wherein: the first electrode film is projected fromthe base to beyond the second electrode film, the second solder film isprojected from the insulating supporting body to beyond the first solderfilm, a trench extends into the insulating supporting body, a portion ofthe first lead electrode film being coplanar with the second leadelectrode film, and another portion the first lead electrode filmextending into the trench, and the first lead electrode film is betweenthe first solder film and the insulating supporting body, and the secondlead electrode film is between the second solder film and the insulatingsupporting body.
 5. A semiconductor light-emitting device according toclaim 4, wherein the thickness of the first solder film is less than thethickness of the second solder film.
 6. A semiconductor light-emittingdevice according to claim 4, wherein the first lead electrode film iselectrically connected to the first solder film, and the second leadelectrode film is electrically connected to the second solder film.
 7. Asemiconductor light-emitting device according to claim 4, wherein thefirst electrode film is electrically connected to the first solder film,and the second electrode film is electrically connected to the secondsolder film.
 8. A semiconductor light-emitting device according to claim4, wherein the first solder film is between the first electrode film andthe first lead electrode film, and the first electrode film is betweenthe base and the first solder film.
 9. A semiconductor light-emittingdevice according to claim 4, wherein the second solder film beingbetween the second electrode film and the second lead electrode film,and the second electrode film being between the base and the secondsolder film.
 10. A semiconductor light-emitting device according toclaim 4, wherein the base includes: a substrate; a contact layer betweenthe substrate and the second electrode; an active layer between thecontact layer and the first electrode, the active layer being adapted togenerate light.
 11. A semiconductor light-emitting device according toclaim 10, wherein the semiconductor chip further includes: a lowercladding layer between the contact layer and the active layer; an uppercladding layer between the active layer and the first electrode.
 12. Asemiconductor light-emitting device including a semiconductor chip, thesemiconductor light-emitting device comprising: a base having thereon afirst electrode film and a second electrode film; and an insulatingsupporting body having thereon a first solder film, a first leadelectrode film, a second solder film, and a second lead electrode film,wherein: the first electrode film is projected from the base to beyondthe second electrode film, the second solder film is projected from theinsulating supporting body to beyond the first solder film, a trenchextends into the insulating supporting body, a portion of the first leadelectrode film being coplanar with the second lead electrode film, thetrench being in the opposite side of the second lead electrode film, andthe first lead electrode film is between the first solder film and theinsulating supporting body, and the second lead electrode film isbetween the second solder film and the insulating supporting body.
 13. Asemiconductor light-emitting device according to claim 12, wherein theportion of the first lead electrode film is between the second leadelectrode film and the trench.
 14. A semiconductor light-emitting deviceaccording to claim 12, wherein the thickness of the first solder film isless than the thickness of the second solder film.
 15. A semiconductorlight-emitting device according to claim 12, wherein the first leadelectrode film is electrically connected to the first solder film, andthe second lead electrode film is electrically connected to the secondsolder film.
 16. A semiconductor light-emitting device according toclaim 12, wherein the first electrode film is electrically connected tothe first solder film, and the second electrode film is electricallyconnected to the second solder film.
 17. A semiconductor light-emittingdevice according to claim 12, wherein the first solder film is betweenthe first electrode film and the first lead electrode film, and thefirst electrode film is between the base and the first solder film. 18.A semiconductor light-emitting device according to claim 12, wherein thesecond solder film being between the second electrode film and thesecond lead electrode film, and the second electrode film being betweenthe base and the second solder film.
 19. A semiconductor light-emittingdevice according to claim 12, wherein the base includes: a substrate; acontact layer between the substrate and the second electrode; an activelayer between the contact layer and the first electrode, the activelayer being adapted to generate light.
 20. A semiconductorlight-emitting device according to claim 19, wherein the semiconductorchip further includes: a lower cladding layer between the contact layerand the active layer; an upper cladding layer between the active layerand the first electrode.